Shape memory embolectomy devices and systems

Abstract

An embolectomy device comprised of an expansion unit and a support unit is disclosed. The expansion unit can be actuated in response to one or more external stimuli, and the support unit, located proximately to the expansion unit, provides a force to hold the expansion unit in place and to further induce the expansion unit's radial expansion. The radial expansion of the expansion unit causes the expansion unit to physically contact a blood clot, enabling the blood clot to be removed. In some embodiments, the expansion unit can be fabricated from a shape memory polymer foam. In some embodiments the support unit can be fabricated from any elastic material including, without limitation, shape memory alloys.

What is claimed is: 
     
       1. A system comprising:
 a pusher rod having proximal and distal ends; 
 a shape memory polymer (SMP) foam slidably coupled to the pusher rod and adjacent the distal end of the pusher rod; and 
 a shape memory (SM) metal coupled to the pusher rod distal to the SMP foam; 
 wherein the pusher rod, the SMP foam, and the SM metal are coupled to each other such that: (a)(i) a distal portion of the SM metal is statically coupled to the pusher rod and a proximal portion of the SM metal is slidably coupled to the pusher rod; (a)(ii) in a non-expanded configuration the SM metal and the SMP foam each have first maximum diameters orthogonal to the pusher rod; and (a)(iii) in an expanded configuration the SM metal and the SMP foam each have second maximum diameters orthogonal to the pusher rod and greater than the respective first maximum diameters; 
 wherein in the expanded configuration the second maximum diameter of the SM metal is less than the second maximum diameter of the SMP foam. 
 
     
     
       2. The system of  claim 1  wherein (b)(i) in the non-expanded configuration the SM metal and the SMP foam each have first maximum lengths parallel to the pusher rod; (b)(ii) in the expanded configuration the SM metal and the SMP foam each have second maximum lengths parallel to the pusher rod; and (b)(iii) the first maximum length of the SM metal is longer than the second maximum length of the SM metal. 
     
     
       3. The system of  claim 1  wherein the SM metal contracts axially when transitioning from the non-expanded state to the expanded state. 
     
     
       4. The system of  claim 3  wherein (b)(i) in the non-expanded configuration the proximal portion of the SM metal is located a first axial distance away from a distal face of the SMP foam; (b)(ii) in the expanded configuration the proximal portion of the SM metal is located a second axial distance away from the distal face of the SMP foam, and (b)(iii) the second axial distance is greater than the first axial distance. 
     
     
       5. The system of  claim 4  wherein the SMP foam is configured to slide distally and traverse the second axial distance when the pusher rod is moved proximally and a proximal face of the SMP foam abuts an obstacle that resists proximal movement of the SMP foam. 
     
     
       6. The system of  claim 5  wherein when the pusher rod is moved proximally and the proximal face of the SMP foam abuts the obstacle the proximal portion of the SM metal supplies both axial force against the SMP foam and non-orthogonal non-axial force against the SMP foam. 
     
     
       7. The system of  claim 3 , wherein the SM metal comprises at least two struts that couple the distal portion of the SM metal to the proximal portion of the SM metal. 
     
     
       8. The system of  claim 7  comprising a conduit coupled to proximal portions of the at least two struts, wherein the conduit is slidably coupled to the pusher rod. 
     
     
       9. The system of  claim 8  wherein the conduit slides distally along the pusher rod when the SM metal transitions from the non-expanded configuration to the expanded configuration. 
     
     
       10. The system of  claim 8 , wherein the conduit and the at least two struts are all monolithic with each other. 
     
     
       11. The system of  claim 8  comprising an additional conduit coupled to distal portions of the at least two struts. 
     
     
       12. The system of  claim 11  wherein:
 the at least two struts are substantially linear in the nonexpanded configuration and substantially arcuate in the expanded configuration; 
 each of the at least two struts connects directly to the conduit; and 
 each of the at least two struts connects directly to the additional conduit. 
 
     
     
       13. The system of  claim 12  wherein the at least two struts do not contact the distal face of the SMP foam in the non-expanded configuration. 
     
     
       14. The system of  claim 3  wherein the pusher rod passes through the SMP foam and at least a portion of the SM metal when the SMP foam and the SM metal are each in the non-expanded configuration. 
     
     
       15. The system of  claim 14 , wherein a first portion of the pusher rod is proximal to the SMP foam, a second portion of the pusher rod passes through the SMP foam when the SMP foam is in the non-expanded configuration, and a third portion of the pusher rod passes through the portion of the SM metal when the SM metal is in the non-expanded configuration. 
     
     
       16. The system of  claim 15 , wherein the first, second, and third portions of the pusher rod are monolithic with each other. 
     
     
       17. The system of  claim 3 , wherein the SMP foam transitions from the unexpanded configuration to the expanded configuration in response to thermal stimulus. 
     
     
       18. The system of  claim 3 , wherein the SMP foam includes a channel that includes a portion of the pusher rod and by which the SMP foam is slidably coupled to the pusher rod. 
     
     
       19. The system of  claim 3  comprising an sheath, wherein the pusher rod, the SMP foam, and the SM metal are all configured to simultaneously fit within the sheath. 
     
     
       20. The system of  claim 19 , wherein the sheath has a maximum outer diameter and the second maximum diameter of the SMP foam in the expanded configuration is at least 150% of the maximum outer diameter of the sheath. 
     
     
       21. The system of  claim 3 , wherein the pusher rod includes an additional SM metal. 
     
     
       22. The system of  claim 3 , wherein the SMP foam and the SM metal transition to the expanded configuration non-simultaneously. 
     
     
       23. A system comprising:
 a sheath and a pusher rod; 
 a shape memory polymer (SMP) foam slidably coupled to the pusher rod; and 
 a shape memory (SM) metal coupled to the pusher rod distal to the SMP foam; 
 wherein the pusher rod, the SMP foam, and the SM metal are coupled to each other such that: (a) in a first state the pusher rod, the SMP foam, and the SM metal are included in the sheath; (b) in a second state the pusher rod, the SMP foam, and the SM metal are deployed from the sheath and, in response to being deployed from the sheath, the SM metal contracts axially, expands radially, and a proximal-most edge of the SM metal moves away from the SMP foam, (c) in a third state the SMP foam expands radially in response to being deployed from the sheath, and (d) in a fourth state the radially expanded SMP foam slides distally along the pusher rod until a distal face of the SMP foam contacts the radially expanded SM metal. 
 
     
     
       24. The system of  claim 23 , wherein in the fourth state the SM metal supplies both axial force against the SMP foam and non-orthogonal, non-axial force against the SMP foam. 
     
     
       25. The system of  claim 24 , wherein:
 the SM metal comprises a conduit and at least two struts; 
 the conduit is coupled to proximal portions of the at least two struts; and 
 the conduit is slidably coupled to the pusher rod. 
 
     
     
       26. The system of  claim 23 , wherein in the fourth state the SM metal directly contacts the SMP foam and supplies non-orthogonal, non-axial force directly against the SMP foam to promote expansion of the SMP foam away from the pusher rod.